The disclosure relates to a steering system for a motor vehicle having a water ingress detection device for detecting water ingress.
DE 10 2006 051 799 A1 discloses a steering system for a motor vehicle, said steering system being fitted with a detection device for detecting water ingress into the steering box of the steering system. The detection device for water ingress comprises an electrode that protrudes into the steering box and is connected by way of a connecting line to an electrical line of a torque sensor. In the event of water entering into the steering box, the electrode is electrically connected to the ground potential of the steering box, as a result of which the voltage potential of the electrical line of the torque sensor drops, which can be detected by means of an electronic control system.
The object of the disclosure is to provide by means of simple measures a steering system for a motor vehicle in such a manner that it is possible to detect water ingress into a housing of a component of the steering system.
This object is achieved in accordance with the disclosure. The embodiments disclose expedient further developments.
The steering system in accordance with the disclosure that is used in motor vehicles comprises an electric servomotor for generating a servo torque that supports the steering movement and furthermore said steering system comprises a water ingress detection device, with the aid of which it is possible to detect water ingress into a housing of a component of the steering system. The servomotor is connected by way of a coupling device to the steering gear of the steering system, by way of which the steering movement that is predetermined by the driver by way of the steering wheel is converted into the front wheel steering movement. The electric servomotor is controlled by way of a control device in which an electronic power system is located. The magnitude of the supporting servo torque can be made to be dependent upon the steering torque that is determined by way of a steering torque sensor in the steering system.
It is fundamentally possible for water to ingress at various sites in the steering system. By way of example, the steering linkage that is part of the steering mechanism is received in a steering box into which it is possible for water to ingress at various sites, by way of example in the region of the steering shaft that is guided into the steering box, and/or in the region of the connection of the electric servomotor or a transmission that is arranged between the servomotor and the steering mechanism. It is also possible for water to ingress into the motor housing of the servomotor and/or the housing of the control device of the servomotor, in particular in the region of the connection to the steering box or in the connecting region between the motor housing and control device housing.
The water ingress detection device is achieved by virtue of the fact that an electrical detecting line is connected to a phase line for supplying current to the servomotor, wherein the electrical detecting line is used to determine the water level in a water collecting region in the housing that is being investigated. If water is located in the water collecting region in the housing, the electrical resistance changes, which owing to the connection of the detecting line to the phase line of the servomotor leads to a voltage change in the phase line that can be detected. The voltage change is in particular determined by an electronic evaluating system in the control device and can be further processed in the control device by way of which the servomotor is controlled and is supplied with current.
This embodiment has the advantage that the water ingress detection device can be produced using simple measures alone by virtue of the fact that a detecting line is connected to a phase line so as to supply current of the servomotor. Since the phase line is connected to the control device and is controlled by said control device, it is also possible to ascertain the voltage change in the phase line in the control device so that a separate evaluating unit is not required. On the contrary, it is possible to use the hardware that is already present for electric servo support.
The water ingress detection device requires only an electric servomotor in the steering system. Further devices such as for example a torque sensor can in fact be a component of the steering system, however said further devices are not required for detecting water in the housing associated with the steering system.
The electrical detecting line extends, in accordance with an advantageous embodiment, between the phase line and the water collecting region. One end of the detecting line is electrically connected to the phase line, the other end of the detecting line is used for the purpose of closing a current circuit in the event of water ingress so that the detecting line is electrically connected to the ground of the housing. This end of the detecting line protrudes, in accordance with a preferred embodiment, into the water collecting region in the housing, wherein it fundamentally suffices that only the free end of the detecting line protrudes without additional electrodes or sensors. As soon as water is collected in the region and the free end of the detecting line is moistened, the electrical resistance between the detecting line and the walls of the housing is decreased, as a result of which the voltage potential is reduced at least approximately to the ground potential of the housing.
However, other embodiments are also possible in which the detecting line is connected by way of example to an electrode that protrudes into the water collecting region.
In each case it is expedient that the free end protrudes into the water collecting region with a spacing with respect to the delimiting walls. This ensures that a sufficiently high electrical resistance is present between the detecting line and the walls of the housing for the case that no water or only a little water is received in the water collecting region and the free end of the detecting line—or where appropriate an electrode that is connected to the detecting line—is not in contact with the water.
In accordance with an advantageous embodiment, at least two different phase lines are provided for the electric servomotor, said phase lines in each case being connected to an electrical detecting line for detecting the water level in a water collecting region. This renders possible by way of example a redundant embodiment in which the at least two detecting lines protrude into the same water collecting region, wherein a voltage change occurs in each phase line if the allocated detecting line comes into contact with water.
By way of example, embodiments are also possible in which the detecting lines protrude different distances into the water collecting region and consequently set a voltage change in the associated phase lines in the case of different fill levels of water in the water collecting region. Furthermore, it is also possible that the different detecting lines protrude into different water collecting regions so that it is possible to monitor different housings or different housing sections within a housing regarding water ingress.
In accordance with a further advantageous embodiment, a phase line is connected to at least two different detecting lines that either protrude into the same water collecting space or into different water collecting spaces. Also in this case either redundant embodiments or the simultaneous monitoring of different water collecting regions are possible. As soon as one of the detecting lines comes into contact with water, the voltage in the phase line drops.
Moreover, in accordance with a further expedient embodiment an electrical connecting line between the housing, in which the water collecting space is located, and the control device of the electric servomotor is associated with the water ingress detection device. In this manner in the case of a corresponding fill level of water in the water collecting space a closed current circuit is produced by way of the electrical connecting line between the control device and the housing and also the detecting line and the phase line that likewise is connected to the control device.
In accordance with a further expedient embodiment, the electric servomotor is a synchronous motor, by way of example a three-phase synchronous motor. In general, both synchronous motors as well as asynchronous motors are considered. It is possible to use motors with n phases, by way of example the mentioned three phases or 2×3 phases.
The servomotor is preferably embodied as an electrically commutated motor and preferably comprises permanent magnets on the rotor. Each phase of the synchronous motor is allocated a phase line so that altogether three phase lines are available, of which one or multiple phase lines are connected to detecting lines in order to be able to monitor the fill level in one or multiple water collecting spaces in one or multiple housings of the steering system.